Group Size and Others' Strategy in an N-Person Game

The effects of group size and cooperativeness of others upon an individual's propensity to cooperate is studied using the Take-Some format of the Prisoner's Dilemma game. By holding utility effects constant, this format permits comparisons to be made between the performances of subjects in different size groups. A 2 × 2 experimental design was employed in which 48 male subjects were assigned to stooge-player groups comprised of either two or eleven “others.†Stooge players in these groups employed either high or low cooperative strategies in 200 repeated trials of play. The results show a significant group-size effect upon the degree of cooperativeness evidenced by the subjects. A significant group size x stooge strategy interaction was also observed, subjects in the 3-person group being responsive to the “others†while subjects in the larger group remained relatively unaffected by “others' â€cooperativeness. An interpretation of these results is made in terms of the “accountability†of an individual to others in the group.